Extremeley rarely. This year it sleeted half an inch on April 7, 2011. But it hasn't snowed officially in 14 years. The closest place where it does snow is Mount Diablo.
Concord,CA and Walnut Creek,CA
Walnut Creek (and the entire Bay Area) had significant snow in January, 1976.
The Infrared Data Association was incorporated in Walnut Creek, CA. The corporate address is P.O. Box 3883, Walnut Creek, CA. Their website is www.irda.org.
Here is the detailed listing of 34 trailer rental companies from Walnut Creek: http://local.sanfrancisco.com/walnut-creek+ca/car+rental/distance.30.26060501.all.zq.html
cost plus
The address of the Lindsay Wildlife Museum is: 1931 1St Ave, Walnut Creek, CA 94597-2540
The address of the Ruth Bancroft Garden is: 1552 Bancroft Rd, Walnut Creek, CA 94598-2361
The address of the Philippine Folklife Museum Foundation is: 305 Drayton Ct, Walnut Creek, CA 94598
The address of the Shadelands Ranch Historical is: 2660 Ygnacio Valy Rd, Walnut Creek, CA 94598-3445
It is 418 miles according to Google Maps.
The Ygnacio Valley Library is located at 2661 Oak Grove Rd, Walnut Creek, CA 94598.
The address of the Massilia Foundation For Art And Culture is: Po Box 2608, Walnut Creek, CA 94595-0608